z boson production and properties at lhc -...

EPS Conference, Manchester 2007

Z Boson Production and Properties at LHC

Matthias Schott*on behalf of the

ATLAS and CMS Collaborations

*[email protected] Experiment

LMU Munich Germany

Slide Slide 11IntroductionIntroduction Signal Selection Total Cross Section Asymmetries Conclusion (Backup)Signal Selection Total Cross Section Asymmetries Conclusion (Backup)

LMU Munich, Germany

Z Boson Production at the LHC

Large Hadron ColliderLarge Hadron Collider

Proton Proton CollisionsProton Proton CollisionsProton Proton CollisionsProton Proton Collisions

√s = 14 TeV√s = 14 TeV

Low Luminosity Phase: Low Luminosity Phase: yyL = 10L = 103333 cmcm--22ss--11

Z boson production via DrellZ boson production via Drell--Yan Yan processprocessprocessprocess

Theoretical crossTheoretical cross--section calculation section calculation available for NNLOavailable for NNLO

Initial Phase of LHC: Initial Phase of LHC: ∫∫ 11

nbZpp 019.0972.1)/( * ±=→→ μμγσ

∫Ldt=100pb∫Ldt=100pb--11 ((≈ 100.000 Z≈ 100.000 Z→→µµµµ))

200.000 Z→µµ events are expected 200.000 Z→µµ events are expected per day during low luminosityper day during low luminosity


p y g yp y g y

ATLAS and CMS Detector

ATLAS DetectorATLAS Detector CMS DetectorCMS Detector

TrackerTracker |η|<2.5 coverage[GeV] 01.0p105p/ T

5T ⊕⋅≈ −σ

|η|<2.6 coverage005.0p105.1p/ T

5T ⊕⋅≈ −σ

EM CalorimeterEM Calorimeter |η|<4.9 coverage |η|<4.9 coverage[GeV] /%10E/ E≈σ E/%52E/ −≈σ

HAD CalorimeterHAD Calorimeter |η|<4.9 coverage |η|<4.9 coverage[GeV] 03.0/%50E/ ⊕≈ Eσ 05.0/%100E/ ⊕≈ Eσ


Muon SpectrometerMuon Spectrometer |η|<2.7 coverage, 1TeV muons: |η|<2.6 coverage, 1TeV muon: 07.0p/ T ≈σ 10.0p/ T ≈σ(standalone) (standalone)

Z Boson Production at the LHC

Physics Measurements Detector Calibration

D t tD t t Effi i iEffi i iCrossCross--SectionsSections

PDFPDF ConstraintsConstraints

F dF d B k dB k d A t iA t i

DetectorDetector EfficienciesEfficiencies

ReconstructionReconstruction

TriggerTriggerForwardForward BackwardBackward AsymmetriesAsymmetries

SensitivitySensitivity toto exoticexotic physicsphysicsprocessesprocesses

TriggerTrigger

ResolutionResolution

AlignmentAlignmentpp AlignmentAlignment

InIn thisthis talktalk::

CrossCross SectionSection MeasurementMeasurement inin thethe muonmuon decaydecay channelchannel forfor thethe initialinitial phasephase

∫=→+→ XZpp BackgroundCandidates* )f-(1N

)/( μμγσ

ForwardForward BackwardBackward AsymmetriesAsymmetries inin thethe electronelectron decaydecay channelchannel∫

→+→Ldt

XZpptotal

)/(ε

μμγσ


Signal Selection

BackgroundBackground ProcessesProcesses

QCDQCD PP

ATLAS(Preliminary)

Xbb +→ μμQCDQCD ProcessesProcesses Xbb +→ μμ

jetsjetsW +→+ μυ

μυμυττ +→→Z

BackgroundBackground UncertaintyUncertainty << 00..002002

μυμυττ +→→Z

jetjetWbWbtt +++→+→ μυμυ

gg yy

ATLAS Selection CMS Selection

TT t t dt t d t kt k OneOne reconstructedreconstructed muonmuon tracktrack ininTwoTwo reconstructedreconstructed muonmuon trackstracks

OppositeOpposite ChargeCharge

||9191..22 GeVGeV--MMµµµµ|<|<3030 GeVGeV

OneOne reconstructedreconstructed muonmuon tracktrack ininthethe muonmuon systemsystem ++ oneone oppositeoppositechargedcharged innerinner tracktrack

||9191 22 GeVGeV MM |<|<77 55 GeVGeV|| µµµµ||

ppTT11>>1515 GeV,GeV, ppTT

22>>2525 GeVGeV

MuonMuon isolationisolation requirementsrequirements

||9191..22 GeVGeV--MMµµµµ|<|<77..55 GeVGeV

ppTT11,,22>>2020 GeVGeV

MuonMuon isolationisolation requirementsrequirements


||ηη|<|<22..55 ||ηη|<|<22..00

In Situ Determination of Detector Response

EfficiencyEfficiency determinationdetermination inin datadata

‘Tag‘Tag andand Probe’Probe’ methodmethod

LimitationsLimitations:: ‘tag’‘tag’ andand ‘probe’‘probe’correlations,correlations, backgroundbackground processes,processes,ФФ--symmetricsymmetric inefficienciesinefficienciesФФ--symmetricsymmetric inefficienciesinefficiencies

DeterminationDetermination ofof detectordetector resolutionsresolutions

FoldingFolding thethe MonteMonte CarloCarlo predictedpredictedFoldingFolding thethe MonteMonte CarloCarlo predictedpredictedresolutionresolution byby aa smearingsmearing functionfunction totoreproducereproduce thethe measuredmeasured ZZ bosonbosonresonanceresonance curvecurve

Expected precision

ΔεΔεTrackingTracking ≈≈ 00..22--00..55%%

CMS

ΔεΔεTriggerTrigger ≈≈ 00..22%%

momentummomentum scalescale toto fewfew perper millemille


……

Further Systematic Uncertainties

FurtherFurther ExperimentalExperimental SystematicSystematicUncertaintiesUncertainties

misalignmentmisalignment

magneticmagnetic fieldfield knowledgeknowledge CMScollisioncollision pointpoint uncertaintyuncertainty

pilepile--upup effectseffects

underlyingunderlying eventsevents

AnAn overalloverall systematicsystematicuncertaintyuncertainty ofof lessless thanthan 00 3535%%uncertaintyuncertainty ofof lessless thanthan 00..3535%%forfor bothboth detectorsdetectors

TheoreticalTheoretical SystematicSystematic UncertaintiesUncertaintiesCMS

PDFPDF choicechoice:: ≈≈ 00..99%%

InitialInitial statestate radiationradiation:: ≈≈ 00..22%%


ppTT effectseffects (LO(LO toto NLO)NLO):: ≈≈ 11..88%%

Summary of Uncertainties

ATLAS (Preliminary) CMS

ΔεΔε ≈ 0 6%≈ 0 6%ΔεΔεReconstruction Reconstruction ≈ 0.6%≈ 0.6%((Uncertainty of muon rec. eff.)Uncertainty of muon rec. eff.)

ΔεΔεKinematicKinematic ≈ 0.3% ≈ 0.3%

ΔεΔεTracking Tracking ≈ 1.0%≈ 1.0%((Uncertainty due to muon Uncertainty due to muon tracking)tracking)

(Uncertainty of kinematic cuts)(Uncertainty of kinematic cuts)

ΔεΔεTrigger Trigger ≈ 0.2%≈ 0.2%(Trigger uncertainty(Trigger uncertainty ))

ΔεΔεTrigger Trigger ≈ 0.2%≈ 0.2%(Trigger uncertainty)(Trigger uncertainty)(Trigger uncertainty(Trigger uncertainty ))

ΔεΔεIsolationIsolation ≈ 0.2% ≈ 0.2% (Uncertainty of muon isolation)(Uncertainty of muon isolation)

ΔεΔεIsolationIsolation ≈ 0.2% ≈ 0.2% (Uncertainty of muon isolation)(Uncertainty of muon isolation)

CMSCMS:: ExpectedExpected PrecisionPrecision forfor ∫Ldt=∫Ldt=100100pbpb--11

*Δσ (lumi)1.0(th.sys)02.0(ex.sys)011.0(stat)004.0)/( * ±±±=→+→Δ μμγσσ XZpp

ATLASATLAS:: ExpectedExpected PrecisionPrecision forfor ∫Ldt=∫Ldt=100100pbpb--11 (preliminary)(preliminary)


0.1(lumi)s)0.02(th.sy(ex.sys) 008.0(stat) 004.0)/( * ±±±=→+→Δ μμγσσ XZpp

Forward and Backward Asymmetries at the Z Pole

ӨӨ--dependencedependence ofof crosscross--sectionsection All events

Events with quark direction correctly estimatedcorrectly estimated

AssumptionAssumption forfor pppp--collisionscollisions:: thethe quarkquarkdirectiondirection isis thethe samesame asas thethe boostboost ofof thethe ZZ

CorrectCorrect forfor largelarge didi--leptonlepton rapiditiesrapidities

OnlyOnly EMEM calorimenterscalorimenters provideprovide thetherequiredrequired largelarge ηη coveragecoveragerequiredrequired largelarge ηη--coveragecoverage

DeterminationDetermination ofof AAFBFB isis aa ‘simple’‘simple’ countingcountingproblemproblem Only

AA statisticalstatistical precisionprecision ofof thethe WeinbergWeinbergangleangle ofof 1010--44 atat ∫Ldt=∫Ldt=100100fbfb--11 reachablereachable..

DominatingDominating systematicsystematic:: PDFPDF UncertaintiesUncertainties

Forward Electrons

All Events


DominatingDominating systematicsystematic:: PDFPDF UncertaintiesUncertainties→→ UseUse AAFBFB toto constrainconstrain PDFsPDFs

Conclusion and Outlook

TheThe ZZ bosonboson willwill bebe producedproduced withwith extremelyextremely highhigh statisticsstatistics

ExcellentExcellent (online)(online) calibrationcalibration channelchannel forfor thethe muonmuon systemssystems andand thethe( )( ) yyelectromagneticelectromagnetic calorimeterscalorimeters

TheThe ppTT andand rapidityrapidity distributiondistribution ofof thethe ZZ bosonboson willwill openopen newnew possibilitiespossibilities totoconstrainconstrain thethe PDFPDF functionsfunctionsconstrainconstrain thethe PDFPDF functionsfunctions

MeasurementMeasurement ofof thethe forwardforward backwardbackward asymmetryasymmetry possiblepossible

InitialInitial PhasePhase ofof LHCLHC

CrossCross sectionsection measurementmeasurement isis expectedexpected toto bebe alreadyalready dominateddominated bybyCrossCross sectionsection measurementmeasurement isis expectedexpected toto bebe alreadyalready dominateddominated bybytheoreticaltheoretical uncertaintiesuncertainties

IndependentIndependent CMSCMS andand ATLASATLAS studiesstudies givegive similarsimilar expectedexpected precisionprecision

PossiblePossible crosscross--checkcheck ofof measuredmeasured integratedintegrated luminosityluminosity


20082008:: Let’sLet’s hopehope toto publishpublish firstfirst resultsresults withwith realreal datadata toto demonstratedemonstrate thethe powerpowerofof thethe ATLASATLAS andand CMSCMS detectorsdetectors

References

CMSCMS

CMSCMS PhysicsPhysics TechnicalTechnical DesignDesign ReportReport VolumeVolume IIIICMSCMS PhysicsPhysics TechnicalTechnical DesignDesign Report,Report, VolumeVolume IIII

CMSCMS NoteNote:: MeasurementMeasurement ofof ZZ→µµ→µµ andand WW→→µµνν inin CMSCMS

FurtherFurther contactcontact personspersons:: JJ.. Alcaraz,Alcaraz, MM..Spiropulu,Spiropulu, RR.. Tenchini,Tenchini, MM.. ThomasThomaspp ,, p p ,p p , ,,

ATLASATLAS

CSCCSC--NoteNote:: MeasurementMeasurement ofof thethe W/ZW/Z (to(to bebe publishedpublished AugustAugust 20082008))

ATLASATLAS--NoteNote:: ForwardForward--BackwardBackward ChargeCharge AsymmetryAsymmetry inin ZZ productionproduction atat thetheLHCLHC

FurtherFurther contactcontact personspersons:: MM.. Aharrouche,Aharrouche, MM.. Boonecamp,Boonecamp, II Boyko,Boyko, LL.. DiDiCiaccioCiaccio TT LeCompteLeCompteCiaccio,Ciaccio, TT.. LeCompteLeCompte


Backup SlidesBackup SlidesBackup SlidesBackup Slides


Differential Cross Section

TheThe PDFPDF acceptanceacceptance uncertaintiesuncertainties ononthethe totaltotal crosscross sectionsection measurementmeasurement areare

ff ff

ATLAS(Preliminary)

anan artefactartefact ofof measuringmeasuring thethe crosscross--sectionsection inclusivelyinclusively ∫Ldt=50pb-1

StudyStudy alsoalso thethe differentialdifferential crosscross sectionsectionwithwith ∫Ldt=∫Ldt=100100pbpb--11

AcceptanceAcceptance uncertaintiesuncertainties areareAcceptanceAcceptance uncertaintiesuncertainties areareexpectedexpected toto bebe veryvery smallsmall

StatisticalStatistical uncertaintiesuncertainties arearet dt d tt d i td i t d id i i iti li iti l hep ph/0508215expectedexpected toto dominatedominate duringduring initialinitial

phasephase

PossibilityPossibility toto studystudy dynamicsdynamics ofof

hep-ph/0508215

yy yy yyQCDQCD andand PDFsPDFs

EE..gg.:.: AA possiblepossible firstfirstobservationobservation ofof xx broadeningbroadening


observationobservation ofof xx--broadeningbroadeningeffecteffect inin hadronhadron collisionscollisions

Background Estimation from Data

EstimationEstimation ofof WW backgroundbackground

AssumptionAssumption

ATLAS(Preliminary)

PP33µµ(Z→µµ)(Z→µµ)≈≈ PP22µµ((W→µW→µνν))

PP33µµ(Z→µµ)(Z→µµ):: ProbabilityProbability forfor 33candidatecandidate muonsmuons passingpassing thetheselectionselection cutscuts inin Z→µµZ→µµ..

EstimationEstimation ofof QCDQCD backgroundbackgroundEstimationEstimation ofof QCDQCD backgroundbackground

SelectSelect subsub--samplesample inin datadata whichwhichisis dominateddominated byby QCDQCD--events,events,ee gg 22 nonnon isolatedisolated muonsmuons

Mµµ for 2 non isolated muons [GeV]

ee..gg.. 22 nonnon--isolatedisolated muonsmuons

UseUse thisthis subsub--samplesample toto estimateestimatethethe QCDQCD backgroundbackground withwith fullfull

Background contribution (ATLAS)

ffbbbb ≈≈ 00..002002 ±± 00..002002 (sys)(sys)

selectionselection cutscuts

OtherOther backgroundbackground processesprocesses arearewellwell understoodunderstood andand cancan bebe

ffWW ≈≈ 00..002002 ±± 00..001001 (sys)(sys)

fftttt ≈≈ 00..00430043 00..001001 (sys)(sys)

Si ilSi il ltlt ff CMSCMS


wellwell understoodunderstood andand cancan bebeestimatedestimated withwith MonteMonte CarloCarlo..

SimilarSimilar resultsresults forfor CMSCMS

Backup Slides

ATLAS(Preliminary)

ATLAS(Preliminary)

Mµµ for 2 non isolated muons [GeV]

ATLAS(Preliminary)


( y)

z boson production and properties at lhc -...

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